How to Convert a Hard Drive from MBR to GPT or GPT to MBR without Losing Data?

March 26, 2019

This article gives a brief introduction of MBR and GPT and tells you how to convert a hard drive from MBR to GPT or GPT to MBR without data loss via AOMEI Partition Assistant.

About MBR and GPT Disk

You may find that sometimes you need to convert MBR to GPT disk, but sometimes, you need to convert GPT to MBR disk. Why? Here we will introduce you about MBR and GPT disk first.  

MBR - Master Boot Record: it is a guide sector in the very front of the drive. It was named in 1983 when partitioning the hard disk or flash disk of IBM compatible personal computer. At that time, PC DOS 2.0 was able to support hard disk. MBR describes the information of logical, including file system and organization type. Besides, MBR also contains the executable code produced when the computer loads operating system in the second stage of start or the boot record connecting every partition (VBR). Such MBR is usually called boot routine.

Note: MBR cannot exist in a media which cannot be partitioned, such as soft disk.

GPT - GUID (Globally Unique Identifiers) Partition Table: it is a new standard of disk partition table originating from EFI (Extensive Firmware Interface). Compared with MBR, it provides a more flexible disk partition principle.

What are the limitations of MBR disk?

  1. MBR disks support up to 2TB partition size only and support four primary partitions only. If partition size surpasses 2TB, the rest space will show as unallocated space.

  2. If more partitions are needed, you have to build a secondary structure known as an extended partition, and then you can create logical partitions on the extended partition. 

  3. MBR partitioning rules are complex and poorly specified.

What are the advantages of a GPT disk?

  1. It can make full use of a very large size to break the 2TB limit of MBR disks.

  2. GPT disks allow an almost unlimited number of partitions. Though Windows implementation restricts the number to 128, it is completely sufficient for use.

  3. Each GPT partition has a unique identification GUID and a partition content type and you can have more primary partitions.

  4. There is almost no partition size limit here. The sector is numbered by a 64-bit integer. A partition with a such number of sectors, can it be small?

  5. Partition on GPT disk has a self-contained backup which is stored on the end of the disk while the original one is saved on the start. When one of the two is destroyed, you can restore it with the other.

  6. Every partition on GPT disk can have a name which is different from partition label.

Why Do You Need to Convert MBR Disk to GPT Disk or GPT Disk to MBR Disk?

As for the differences between MBR disk and GPT disk, you may need to convert GPT to MBR disk, or convert MBR to GPT disk for better usage.

1. Convert MBR to GPT for full using

As mentioned above, MBR disks only support up to 2TB partition size, so if you have a disk which is MBR formatted and larger than 2TB, you can only use 2TB disk size among it, but the rest of it can not be used. Or when you need to create more than four primary partitions, converting MBR disk to GPT disk is necessary to make full use of the disk space.

2. Convert GPT to MBR for system compatibility

On the other hand, since Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, or Windows XP 32-bit version does not support GPT partitions, a GPT disk will display as GPT protective partition in these systems, thus you can not access the data until you convert it back to MBR disk. In such situation, you have nothing to do but to convert GPT to MBR disk. 

3. Windows cannot be installed to this disk error

Sometimes you may encounter an error message “Windows cannot be installed to this disk. The select disk is of GPT partition style”. To fix this error, you need to convert GPT to MBR before installing the system. While in other situations, you may get the error: “Windows cannot be installed to this disk. The select disk is of MBR partition style”. For this circumstance, you need to convert MBR to GPT partition style.

How to Convert a Data Drive from MBR to GPT or GPT to MBR without Losing Data?

Free download AOMEI Partition Assistant Professional to have a try. Windows 10/8/7 is supported. If you are working with Windows Server 2003, 2008, 2012, 2016, 2019, you can apply AOMEI Partition Assistant Server edition.  

Step 1.  Install and run AOMEI Partition Assistant Professional. If the disk you want to convert is an MBR disk, right click it, select "Convert to GPT disk" function in the drop-down menu. If the disk you want to convert is a GPT disk, right click it, select "Convert to MBR disk" function in the drop-down menu. Let's take converting MBR disk to GPT disk as an example.

Convert Data Disk to GPT

Step 2. Click "OK" after confirming the operation.

OK to GPT Data Disk

Step 3. You can preview the conversion. To save the change, please click "Apply" on the toolbar and wait for the process to complete.

Apply to GPT Data Disk

AOMEI Partition Assistant Professional also allows you to convert system disk between MBR disk and GPT disk without losing data. Click it and you can follow the steps to perform it.


  • AOMEI Partition Assistant can convert system disk between MBR and GPT partition style without losing data. But in case of some unexpected accidents which may cause data loss, you need to backup system before converting.

  • Converting system disk from MBR to GPT needs your computer's motherboard that supports EFI/UEFI boot mode. After converting, you need to change boot mode from Legacy BIOS to UEFI, otherwise, your PC won't boot successfully.

  • For conversion between MBR and GPT disks on Laptop, please make sure the power supply is sufficient.

  • To ensure the data is consistent, do not abnormally terminate the program during the conversion process.

  • If you want to convert any larger than 2TB GPT disk back to MBR disk, you'd better ensure that the data does not account for space more than 2TB. Otherwise, the overloaded data will get lost. However, if you really want to convert your GPT drive on which there are more than 2TB data into MBR disk, you can transfer the extra data to other places via a data migration software before converting.

  • If there is no system on the PC but you want to convert the disk connected to the PC from MBR to GPT or GPT to MBR, then you can make bootable media with AOMEI Partition Assistant on a PC that can boot normally. After that, you can boot the PC that has no system from this bootable media and AOMEI Partition Assistant's interface will be loaded so that you can perform the corresponding operations.